The delivery of therapeutic agents to the inner lining of vessel walls can be very effective to address various types of vascular injury. A key consideration for such procedures is the precise delivery of a predetermined amount of therapeutic agent. Some methods of delivery present challenging manufacturing processes in order to control the amount of therapeutic agent on the delivery device. For example, dip coated catheter balloons (percutaneous transluminal angioplasty (PTA) catheter balloons) can present several drawbacks during manufacturing. Application of a uniform coating can be difficult when using the dipping process as the process may be very labor intensive and time consuming.
Further, in other devices fluids are metered through weeping orifices within an inflatable balloon to provided localized delivery of the fluid (e.g., therapeutic agents or contrast media). This configuration requires filling the inflatable balloon with the infused fluid. In some examples, the infused fluid is a toxic substance with localized therapeutic benefits to the vessel. It is difficult to meter the flow of the infused fluid through weeping orifices that expand and contract to some degree with deployment and storage of the balloon through inflation. For example, a specified pressure must be maintained to inflate the balloon. The specified pressure for inflation may administer the infused fluid at too great a flow rate to the vessel with attendant risks (e.g., overdosing of the infused fluid, delivery of supplemental infused fluid downstream from the desired treatment site and the like).
Additionally, with smaller weeping orifices the infused fluid may plug the orifices and prevent the precise delivery of the desired dose of the fluid. Further still, where expensive agents, such as pharmaceuticals, are used it is expensive to use the agent as the media for inflation of a balloon, a relatively large volume, as compared to the small volume of agent required for delivery to the desired treatment location. The volume of agent used to inflate the balloon is often not recoverable thereby greatly enhancing the cost of the procedure.